Heaphy Track Transport

Hi. Our Aug Heaphy tramp just got a bit more complicated since Golden Bay Air will not be operating then, as we had been counting on. We will have a rental car, which has its own complications (insured drivers). Does anyone have any suggestions on other ways that our family can make this loop happen? Is there a bus / private shuttle service that might be able to get us from Kohaihai back to Takaka? Thanks for any tips.